Rosin base ester-drying oil



Patented Feb. 29, 1944 UNITED .sTATE s] PATENT OFFICE T ROSIN BASE ESTER-DRYING OIL COMPOSITION Frank G. Oswald, Newark, DeL, assignor to Hercules Powder Company, Wilmington, corporation of Delaware DeL, a

No Drawing. Application April 22, 1941, L Serial N0. 389,741

1 Claim.

.This invention relates to the cooking of dry-' nish industry. Inexpensive varnishes have been prepared by bodying the soft oils with various ester gums at cookingJemperatures below at most about 575 F. to avoid discoloration. However, such varnishes have not had the excellent characteristics of the tung oil varnishes, the soft oil varnishes bodying very slowly in the kettle, and forming films whichdried slowly to relatively soft films of low water and alkali resistance.

It is an object of, this invention to provide a process for preparing improved soft oil-rosin base ester compositions. It is an object of this invention to provide a process for producing varnish-compositions from the soft oils improved with respect to bodying time and to the effect of the bodying on the properties of the bodied 'oil produced.

A further object of this invention is to provide an extremely simple and economical method for producing softoil-rosin base ester compositions of improved properties.

Other objects of this invention will 'appearcontact with a rosin base ester of pentaerythritol vor 9. polypentaerythritol to a temperature substantially above the normal cooking temperature of a soft oil-rosin ester varnish mixture, and maintaining the temperature above this limit for a period of time suflicient to produce a composition bodied to a predetermined viscosity.

The soft oils which may be cooked at high temperatures with the pentaerythritol esters according to the process of this invention are any of those drying oils such as linseed oil, dehydrated castor oil, soybean oil, perilla oil, poppy seed oil and similar oils which do not ordinarily produce varnishes which dry rapidly to hard water-resistant films, or mixtures of such oils. If desired the process according to this invention may be applied to the soft drying oils in admixture with fast drying oils such as tung oil. The characteristics of the varnish compositions produced, and the cooking time necessary, will be dependent on the exact composition of the drying oil or drying oil mixture employed, the. faster drying oils or mixtures producing varnishes bodying relatively quickly in the kettle and producing compositions of greatest hardness and alkali and water resistance. However, it will be advisable not to employ an excessive proportion of very fast drying oils in preparing compositions according to this invention since this may result in gelling of the composition in the kettle, especially at relatively high cooking temperatures.

The drying oils or their mixtures employed may desirably be prebodied prior to the cooking with the rosin base ester, thus allowing a heat bleach of the drying oil and helping to shorten the cooking time with the rosin base ester necessary to give the desired body.

In cooking the soft oils according to the process of this invention any of the oil-soluble rosin base esters of pentaerythritol or a polypentaerythritol such as dipentaerythritol, or mixtures of such alcohols may be employed. By rosin base esters is herein meant esters whose acid component comprises any of the rosin acids or modified rosin acids such as the rosin acids comprising gum rosin, wood rosin, heat treated rosin, Hyex (disproportionated) rosin, hydrogenated rosin,- polymerized rosin, etc. The rosin base esters may include mixed esters such as, for example, the esters comprising esters of rosin acids and unsaturated polybasic acids such as maleic acid or anhydrlde, fumaric acid, etc., saturated polyl'basic acids such as phthalic acid, succinic acid, etc., or fatty acids such as linseed oil fatty acids. etc. The rosin base esters of pentaerythritol or polypentaerythritol are extremely heat stable and may be employed in the varnish cooking at the high temperatures employed according to this invention without substantial discoloration of the bodying oil. While any such ester may be employed, in general it will be preferable to employ the higher melting and the harder and tougher resins since such resins generally yield varnish compositions most improved in properties.

According to this invention the pentaerythritol or polypentaerythritol esters and soft oils are cooked at temperatures substantially above those normally used in cooking drying oils with ester gums, and preferably within the range of 575-625 F. These elevated cooking temperatures have been found possible because of the extremely high heat stability of the pentaerythritol or polypentaerythritol esters described, enabling their use at such cooking temperatures without substantial discoloration while other esters such wide variety of predetermined properties.

as the rosin glycerides would cause marked discoloration of the varnish at these cooking temperatures. By cooking'at the high temperatures of this invention, the cooking time necessary to give the varnish composition the necessary structure or body" is substantially reduced to relatively short periods as is illustrated in the examples which follow. However, the new cooking process has its greatest advantage over prior low temperature cooking processes in its effect on the properties of the varnish composition produced. Thus the varnish compositions produced according to the process of this invention dry more rapidly to harder and more alkali resistant films than the corresponding varnish compositions produced from the same drying oils and pentaerythritol esters or other ester gums by cooking according to the prior lower temperature cookingprocesses. Moreover, the varnishes produced according to this invention may compare favorably in such properties to the very expensive tung oil varnishes. The advantages which may be realized by the process of this invention depend, to some degree, on the specific temperatures employed and, in general, cooking at the highest possible temperatures produces the most favorable results. Although some improvement over the low temperature cooking process may be obtained by using even slightly higher temperatures, it will be desirable to employ cooking temperatures of at least about 575 F. in order to realize substantial improvement over the ordinary low temperature process generally carried out at temperatures well below 575 C. However,

it will be perferable to employ cooking tempera--' tures of at least about 585 C. in order that the marked advantages oiiered by the process of this invention may be fully attained. On the other hand, the temperature will preferably be maintained below about 625 F. as an upper temperature limit in order to avoid any discoloration or extensive decomposition of the varnish mixture, and to avoid the danger of carrying the cooking to temperatures above the flash point of the mixture where open kettles are employed.

While. the compositions prepared according to this invention serve as excellent varnishes alone, they may be mixed in any suitable manner with other varnish compositions, drying oils, resins, etc., in order to produce compositions having a Thus, varnish compositions which dry rapidly to films of excellent durability, gloss, alkali resistance, etc.; have been prepared by cooking the varnish compositions prepared according to this invention with small quantities of tung oil at relatively low temperatures.

The following examples will serve to illustrate various embodiments of this invention:

Example 1 A varnish was prepared from a wood rosinpentaerythritol ester and a prebodied linseed oil. The wood rosin-pentaerythritol ester employed had an acid number of 15, a drop melting point of 114 C., and a color grade N Standard U. S. Rosin Type. The linseed oil employed was prebodied as follows: The raw alkali refined linseed oil was heated to 450 F. in one hour and maintained at this temperature for one hour. The temperature was then raised to 600 F. in 1 hours, and held at 600 F. for 15 minutes to induce a heat bleach in the oil. The temperature was then dropped to 575 F. and held at this temperature for 4 hours. The linseed oil was thus bodied to a Z-3 viscosity on the Gardner-Holdt scale. One hundred pounds of the resin were added to 25 gallons of the linseed oil which had been prebodied to a viscosity of Z-3. This mixture was heated to a temperature of 590 F. over a /2 hour period of time, then held at this temperature for 2 hours at which point a cold pill of the varnish showed a gel-like structure. The varnish was then cooled to 450 F., and thinned with enough mineral spirits to bring the solids concentration to 50%. The varnish at this concentration had a viscosity of B on the Gardner- Holdt scale, and a Hellige color of 4L. The varnish formed films having a dry time, alkali and water resistance greatly superior to corresponding varnishes cooked at 570 F., and to the glyceryl ester gum varnishes made with soft drying oils.

Example 2 A varnish was prepared from a prebodied linseed oil and the ester of polymerized rosin and maleic anhydride with a crude mixture of alcohols comprising about 25% dipentaerythritol andpentaerythritol. This resin was prepared by esterifying 3.5 parts by weight of maleic anhydride and parts by weight of a polymerized rosin having a drop melting point of 100 C., with 13.5 parts by weight of the alcohol mixture, and removing volatile materials at the end of the reaction. The resin had a drop melting point of 155, and a color of M, Standard U. S. Rosin Type.

One hundred pounds of this resin was added to 25 gallons of linseed oil prebodied to a viscosity of Z-3 on the Gardner scale. Thismixture was heated to a temperature of 595 F. over a /g hour period, then held at this temperature for 2 hours and 40 minutes or until a cold pill of the varnish showed a gel-like structure. The varnish was then cooled to 450 F. and thinned to 50% solids with mineral spirits. At this concentration the varnish had a viscosity of N on the Gardner Scale and a Hellige color of 6. This varnish formed films having a dry time, alkali and water resistance greatly superior to corresponding varnishes cooked at 570 F. top heat, and to theordinary glyceryl ester gum varnishes, and approximately equal to corresponding 25-gallon este gum-tung oil varnishes.

Example 3 A varnish was prepared from a prebodied dehydrated castor oil and a wood rosin ester of a crude pentaerythritol-dipentaerythritol mixture containing approximately 25% dipentaerythritol and 75% pentaerythritol. The rosin ester had an acid number of 15, a drop melting point of 128 C. and a color of N Standard U. S. Rosin Type. One hundred pounds of this rosin ester were added to 25 gallons of the dehydrated. castor oil prebodied to a viscosity of Z-3 on the Gardner scale. This mixture was heated to a temperature of 595 F. over a hour period of time, then held at this temperature for l -hours or until a cold pill of the varnish showed a gel-like structure. The varnish was then cooled to 450? F. and thinned to 50% solids with mineral spirits. At this concentration the varnish had a viscosity of E on the Gardner scale and a Hellige color of 6. This varnish formed films having a dry time, alkali and water resistance greatly superior to corresponding varnishes cooked at 570 F., and

approximately equal to corresponding 25-gallon glyceryl ester gum-tung oil varnishes.

It will be understood that the details and examples hereinbefore set forth are illustrative only and that the invention as broadly described and I 'of 25 gallons of the oil to 100 pounds of the said pentaerythritol ester, at a. temperature of about 590 F. until a chilled drop of the mixture becomes gelled, cooling the resulting mixture and 5 thinning it with mineral spirits in an amount to form a varnish having about 50% solids content.

mm G. oswAm. 

